Implanting an electrode array against the spinal cord inside the dura for stimulating the spinal cord and treating pain

Abstract

A method for treating intractable pain via electrical stimulation of the spinal cord. Remote, non-contact stimulation of a selected region of spinal cord is achieved by placement of a transceiver patch directly on the surface of that region of spinal cord, with said patch optionally being inductively coupled to a transmitter patch of similar size on either the outer or inner wall of the dura surrounding that region of the spinal cord. By inductively exchanging electrical power and signals between said transmitter and transceiver patches, and by carrying out the necessary electronic and stimulus signal distribution functions on the transceiver patch, the targeted dorsal column axons can be stimulated without the unintended stray stimulation of nearby dorsal rootlets. Novel configurations of a pliable surface-sheath and clamp or dentate ligament attachment features which realize undamaging attachment of the patch to the spinal cord are described.

The invention claimed is: 
     
       1. A method of intradurally implanting an electrode assembly in a subject against the spinal cord, comprising:
 (a) surgically preparing the subject by exposing the dura that surrounds the subject's spinal cord; 
 (b) making an opening in the dura; 
 (c) inserting the electrode assembly though the opening so that a plurality of electrodes on the electrode assembly are placed in direct contact with the surface of the spinal cord at a treatment site inside the dura; 
 (d) securing the electrode assembly such that the electrodes stay in place and the cerebrospinal fluid (CSF) filled space is maintained, thereby sustaining direct contact between the plurality of electrodes and the surface of the spinal cord at the treatment site while allowing CSF to flow between the electrode assembly and the dura; and 
 (e) surgically closing the dura around the electrode assembly. 
 
     
     
       2. The method of  claim 1 , whereby the electrode assembly is secured against the spinal cord at the treatment site such that the electrodes exert generally even pressure on the spinal cord, thereby serving as mechanical anchoring points for the electrode assembly. 
     
     
       3. The method of  claim 1 , whereby the electrode assembly is secured against the spinal cord at the treatment site such that each electrode can move independently in relation to the assembly, thereby accommodating pulsations of the surface of the spinal cord. 
     
     
       4. The method of  claim 1 , which comprises wrapping flexible attachment arms that extend from either side of the backing around the spinal cord. 
     
     
       5. The method of  claim 4 , which comprises implanting a transmitter outside the dura; and wirelessly connecting the transmitter with a receiver circuit in the electrode assembly, thereby configuring the transmitter for wireless transmission of energy to the electrode assembly. 
     
     
       6. The method of  claim 1 , which comprises extending conductors electronically connected with the electrodes out through the dura; and closing the dura around the conductors so as to form a water-tight closure. 
     
     
       7. The method of  claim 6 , whereby the conductors pass from the electrodes to the surrounding dura at positions that are adjacent to left and right dentate ligaments. 
     
     
       8. The method of  claim 6 , further comprising electronically connecting the connectors to a power supply battery and a control circuit that have been implanted subcutaneously in the subject. 
     
     
       9. A method of stimulating the spinal cord in a subject in need thereof, comprising delivering electrical stimulation to the spinal cord of the subject by way of an electrode assembly that has been implanted inside the dura and against the spinal cord of the subject according to the method of  claim 1 . 
     
     
       10. The method of  claim 9 , wherein the electrodes are activated selectively so as to stimulate the subject's spinal cord in a preprogrammed spatio-temporal sequence. 
     
     
       11. A method for treating back pain in a subject, comprising stimulating the spinal cord of the subject according to the method of  claim 9 . 
     
     
       12. A method of intradurally implanting an electrode assembly in a subject against the spinal cord, comprising:
 (a) surgically preparing the subject by exposing the dura that surrounds the subject's spinal cord; 
 (b) making an opening in the dura; 
 (c) inserting the electrode assembly though the opening so that a plurality of electrodes on the electrode assembly are placed in direct contact with the surface of the spinal cord at a treatment site inside the dura; 
 (d) securing the electrode assembly such that the electrodes stay in place without constricting the dura to the spinal cord, thereby sustaining direct contact between the plurality of electrodes and the surface of the spinal cord at the treatment site while accommodating normal movement of the spinal cord within the spinal canal; and 
 (e) surgically closing the dura around the electrode assembly.